The present invention relates broadly to an optical network element.
Existing optical networks incorporating Wavelength Division Multiplexer (WDM) technology have been designed symmetrically, i.e. with provision of the same amount of bandwidth in either transmission direction between network elements.
The main reason for this is that those optical networks were designed for voice communication, which is symmetric by nature. In other words, there is no requirement in voice communication to xe2x80x9cfavourxe2x80x9d one transmission direction over the other through provision of asymmetric bandwidth allocation.
Typically, those symmetric optical networks incorporate separate optical fibre connections for each transmission direction. Alternatively two separate bands are allocated on one optical fibre for the respective transmission directions.
However, in optical networks that are to be utilised for data communication as opposed to primarily voice communication, the nature of the data traffic requirements is typically asymmetric. For example, the communication traffic between a computer connected to the Internet (particularly for private use) is such that a vast amount of data is transmitted to that particular computer, whereas data transmission from the computer into the Internet is typically minimal. In this scenario, utilisation of a symmetric optical network is inefficient, as it represents a wasteful use of optical fibre and/or bandwidth resources.
In at least preferred embodiments, the present invention seeks to provide an optical network element which is compatible with asymmetric communication requirements.
In accordance with a first aspect of the present invention there is provided an optical network element comprising a plurality of subscriber line connections, a WDM unit having a plurality of WDM channel connections, a plurality of subscriber line interface cards and a plurality of trunk line interface cards for optical interfacing between the subscriber line connections and the WDM channel connections, and a switch arranged, in use, in a manner such as to be capable of switching transmission directions between the WDM channel connections and individual ones of the subscriber line connections by suitable switching of an optical path configuration between transmitter ports and receiver ports of the subscriber line interface cards and the WDM channel connections.
Pairs of one subscriber line interface card and one trunk line interface card may be implemented on a single card.
Preferably, the switch is disposed between transmitter and receiver ports of the trunk line interface cards on the WDM side thereof and the WDM channel connections and is arranged in a manner such that, in use, the transmission directions are switched by suitable switching of the connectivity between said transmitter and receiver ports of the trunk line interface cards and the WDM channel connections.
The switch may comprise an optical patch panel arranged, in use, to manually switch said connectivity.
Alternatively, the switch may be automated. The automated switch is preferably an automated optical switch.
In accordance with a second aspect of the present invention, there is provided an optical network element comprising a plurality of full-duplex subscriber line connections and a WDM unit having a plurality of WDM channel connections, the network element being arranged in a manner such that only active transmission direction channels of the full-duplex subscriber line connections are, in use, connected to the WDM channel connections.
In accordance with a third aspect of the present invention there is provided an optical network element comprising a plurality of subscriber line connections and a WDM unit having a plurality of WDM channel connections, the network element being arranged in a manner such that, in use, a transmission direction with respect to transmissions to and from the subscriber line connections is wavelength independent.
In accordance with a fourth aspect of the present invention there is provided an optical network having a plurality of subscriber line connections, the network being arranged in a manner such that, in use, a transmission direction with respect to transmissions to and from the subscriber line connections is wavelength independent.
Preferably, the optical network incorporates an optical network element in accordance with the third aspect of the present invention.
In accordance with a fifth aspect of the present invention there is provided a method of switching transmission directions between WDM channel connections and individual ones of a plurality of subscriber line connections of an optical network element, the method comprising the step of switching an optical path configuration between transmitter ports and receiver ports of subscriber line interface cards of the network element and the WDM channel connections.